I. Field of the Invention
The invention concerns a feeding device installed in the loading bin of a sausage filling machine, and more particularly, to a mechanism for driving a feed screw in the feeding device.
II. Description of Prior Art
The first element of a sausage filling machine consists of a loading bin or hopper that is shaped as a funnel and located at the top of the machine. The sausage meat is loaded in bulk form into this hopper. From there it is pressed into a conveyor which may consist of a pair of screw pumps. At the far end of these screw pumps the sausage meat is then pressed into a filling tube. The other end of the screw pump system is connected to a vacuum exhaust provided with a variable setting allowing the air to be extracted in various amounts from 0% to 99%. This system is usually called a "vacuum filling sausage machine". The vacuum exhaust sucks the air out of the sausage meat, increasing the compactness of the filling, giving a better color to the final product, providing for a longer shelf life of the sausage and assuring a more precise measuring of the fill.
The above-described system results in a continuous filling process; there is no need to establish interruptions in the procedure and the material may be loaded into the bin at intervals.
As the sausage meet emerges from the filling tube, it is pressed into a casing. The selected weight of each sausage link is determined by a controlling device. After a specific weight has been reached, the sausage link is closed off by means of a twisting device which gives a number of turns to a specific length.
The sausage meat may also be dispensed into glass jars or cans instead of a casing. In this case the twisting device is removed from the machine.
Since the sausage meat consists of a relatively tough and viscous material, it is necessary to install a conveying device into the loading bin in order to press the material on its way toward the outlet of the conical end of the hopper. This device consists usually of a helical conveyor or "feed screw" which is affixed to a driven mounting ring or turntable. The mechanism requires a balanced mounting and the corresponding bearings must be designed so as to assure a clean and hygienic process, especially in cases where food items are being handled. Two main designs of feeding devices have been considered:
a) The feed screw is affixed to a geared mounting ring or turntable mounted on bearings. The turntable is driven radially and the axial forces are absorbed by friction rings which also act as sealing gaskets at the upper and lower ends of a conical loading bin. The upper portion of the bin located above the turntable is built so that it may swivel away, allowing for the removal of the turntable with its attached feed screw and sealing rings. This method provides for the easy cleansing of all components of the mechanism. However, it also has the drawback that a play-free execution is difficult to achieve. The existence of mechanical play at the gear teeth generates annoying noises during the operation of the machine, especially at start up, and also increases the wear and tear of the mechanical elements, resulting in downtime for needed repairs and maintenance. Further problems are caused by the eventual invasion of sausage meet into the drive mechanism. Another unfavorable factor consists of the large weight of the turntable and its associated elements. PA1 b) In an alternative design, the feed screw is affixed to a mounting ring or turntable that is mounted on roller bearings with minimum mechanical play. However, this mode of construction does not allow for the removal of the feed screw during the manual cleansing process. Therefore, the feed screw must be cleaned in site, within the loading bin. It thus becomes necessary to assure a good seal of the hopper from the housing that encloses the mechanical drive elements with their corresponding lubricant. This is achieved by using special gaskets that are located at the upper and lower surfaces of the mounting ring. The mechanical design of this alternative provides good stability for the components, a rather play free interaction of the mechanism elements and an almost noiseless operation. The only disadvantage is that an eventual leakage may occur at the sealing gaskets. Thus, the sausage meat may become contaminated with the lubricant of the drive mechanism, or traces of the sausage meat may be introduced into the housing of the drive where it will eventually deteriorate.